404 MARINE INVERTEBRATES 



The entire absence of such important organs as the heart and 

 gills, together with the fact that they are undoubted mollusks, 

 would indicate that the Scapliopoda are very degenerate animals. 

 The circulatory and respiratory S3 r stem of mollusks is typically 

 of a high order. 



A great many specimens of the Dentalidce dredged in New 

 England waters are dead shells, occupied by a worm which seals 

 up the larger opening, leaving only a small aperture through 

 which it protrudes its long white body. These must not mislead 

 the collector into a vain search for a mantle and other molluscan 

 characteristics of anatomy. 



Some of the larger species of Dentalium from deep-sea stations 

 are four to five inches in length. 



